On the Stochastic Analysis of a Quantum Entanglement Distribution Switch
On the Stochastic Analysis of a Quantum Entanglement Distribution Switch
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DOI：
10.1109/tqe.2021.3058058
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发表时间：
2019-03
影响因子：
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通讯作者：
Gayane Vardoyan;S. Guha;P. Nain;D. Towsley
中科院分区：
文献类型：
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作者：
Gayane Vardoyan;S. Guha;P. Nain;D. Towsley
在这篇文章中，我们研究了一个在星星拓扑中为$k$个用户服务的量子纠缠分发交换机。我们的模型变量的系统作为连续时间马尔可夫链，并获得开关容量的表达式，预期数量的量子位存储在存储器中的开关，和量子存储器占用分布。我们获得了一些分析结果的系统中，测量是不完美的，链接是同质或异构的开关，有一个无限或有限数量的量子存储器或缓冲区。此外，我们使用一个简单的模型来模拟量子态的退相干和相关的截止时间对它们的存储的影响。从数值观测中，我们发现退相干相关的截止时间对均匀系统的容量和期望的存储量子比特数的影响很小。对于异构系统，特别是在其稳定区域的边界附近操作的那些系统（即，几乎不稳定的系统）、缓冲器大小和去相干可以对性能度量具有显著影响。我们还了解到，一般来说，将每个链接的缓冲区大小从一个增加到两个量子比特对大多数系统都是有利的，而增加缓冲区大小会进一步减少收益。在这项工作中获得的分析结果可以作为一个有用的指导，对未来的量子开关的设计，通过允许设计者确定多少量子存储器对于给定数量的用户是足够的，以及提供关于这些和类似设备的性能的有价值的洞察。
In this article, we study a quantum entanglement distribution switch that serves $k$ users in a star topology. We model variants of the system as continuous-time Markov chains and obtain expressions for switch capacity, expected number of qubits stored in memory at the switch, and the quantum memory occupancy distribution. We obtain a number of analytic results for systems in which measurements are imperfect, the links are homogeneous or heterogeneous and for switches that have an infinite or finite number of quantum memories or buffers. In addition, we model the effect of decoherence of quantum states and associated cutoff times on their storage using a simple model. From numerical observations, we discover that decoherence-associated cutoff times have little effect on capacity and expected number of stored qubits for homogeneous systems. For heterogeneous systems, especially those operating near the boundaries of their stability regions (i.e., systems that are nearly unstable), buffer size and decoherence can have significant effects on performance metrics. We also learn that in general, increasing the buffer size from one to two qubits per link is advantageous to most systems, whereas increasing the buffer size further yields diminishing returns. The analytical results obtained in this work can serve as a useful guide toward the future design of quantum switches—e.g., by allowing the designer to determine how many quantum memories suffice for a given number of users—as well as provide valuable insight on the performance of these and similar devices.